returning to bantam racing

Thankyou Derek ,
My goodness that is one hell of a performance improvement with no down side to spoil things,
just goes to show what is achievable with appropriate advice and help .
I`ll digest all of your info and get back to you shortly .


Going on to PMs , for the whole of May i have had no contacts at all concerning the subjects
you mention , i`m not sure what is going on , so if anyone has attempted to PM me , their messages
are not in my inbox !
John seems to be experiencing the same problem , can anyone offer an explanation ?

Trevor

Good Evening Trevor,

As daft as it sounds have you checked what capacity your inbox is at with regards to pm's.

Kind Regards

Eddie

Thanks Ed ,
Good suggestion , used volume is only 46% , that would leave spare capacity for many PMs !



regards Trevor

Your welcome Trevor,

May just be a glitch as mine appear to have gone to you.

Regards



Eddie

Hi Trevor No pm's -
I thought you had fallen out with us all!

mind you every one I speak to I tell them to PM you for advise, may be you caught a virus from some far away place !.

I know I have sent you more than a few, Nigel has also confirmed so too has he.

I hope your well Kind regards

what you take on the Carb issue I have, Ihave taken some kind advice from Nick Bramley and Mick Potter so hopefully will resolve that.

I wish to stand still with this bike as its clearley limited in the transfer are I will either re build my other bike and put My alloy barrel or BTW on it to see if I can get a little more power with the same detailed process,

Ihave to try and get my son out know I have an early 50x56 for him finished but for the chassis Iwas wondering if it was one of yours or steve's as I dont know who else built 50x56 motors in the late 70's adrian andrew use to race it ! trying to track down the origin of the owner, its been done very nicely

regards Derek

Hi Trevor

To up date you, CARB- found the problem, seems the pilot system has been affected by the choke not closing off correctly the rubber crumit seal on the end of the choke plunger has been pushed in meaning it has not pressure sealing the sytem from affecting the carburation, while we understand, the system is only the initial start/pilot system, i have been told it does and can affect the entire system, as it alters/affects the tube where atomizing/mixing takes place, this may be the reason why the carburation was so sensitive to the pilot screw movement.

now the wheel bearing seems to have had quite an effect, on the rolling road readings, seems some of what John says is correct, about duplication of results, while this is not a big defference, as the bearing was repackedwith grease at cadwell, i can not say what effect it had, as we are having trouble getting the same readings.

So we fitted another wheel, with a new bearing and tried to duplicate our last reading, we just could not get close the readings were about 10 to11% higher than previous, so we refitted the same wheel with the doggy wheel bearing, blimey reading within .5 hp but no appreciable difference at low speed, so it appears the wheel bearing has been faulty for some time, i dont know why this is so difficult to spot, as its not easily spotted the wheel was always or appeared to be free to spinning by hand, would be interesting to see if others know of a way to detect this, !

Trevor i asked a number of questions by P.M. 1)was would it be ok to publish the formula pipe, you sent me, 2) is it ok to send in the head/squish profile with the nifo and explanation on why, to the rest on here, that you kindly sent me,

if it had the desired effect on all bike as it did with mine surely close up the midfield to the front 3 or 4, i'm absolutly positive about this, i also noticed it does say in all the tuning books about the importance of a minimal squish set accuratly each time.

what do you think.

kind regards Derek

My inbox is relatively free, as Trevor´s -- 62% -- coincidence? or is there a glitch in the workings of Bantam PM software? I mean two months after posting PMs they arrive?? Much like the good old days when a barefoot bloke in Africa, running with a letter in a cleft stick got chased by a lion thus reducing delivery time by several hours -- or not at all...??

My e-Mails section was overloaded. I deleted hundreds of e-Mails into the e-Mail waste paper basket which nicely vanished but when I looked in the Main Waste Paper basket they were not there. Then -- about a week later -- a few days ago -- they were all back on the e-mail´s WPB... So I´ve deleted them again and they must be still floating about somewhere because they are definitely not on the main WPB...
Worries me a bit because I cannot remember what it was I said about Derek...???


I learnt about computers when at Ford Dunton and actually wrote a software programme called, "End of compression-stroke temperature..." but they (Ford Computer Teachers) left out all this other stuff that I have suffered since and been overcome by... but then I have another difficulty also -- this PC and attachments fell-off-a-lorry and the computer language is in Deutsch so I might be using the wrong word to delete or to store....

Maybe I should be using the German for `destroy´ -- must look it up...
Immer Optimistich sein -- ever be optimistic...


Cheers!

Derek ,
First things first , the last PM i have from you is mid April , plenty have appeared from other sources , even from
as far afield as France , Australia and New Zealand , even one from Terry ! From this one might conclude that my
PM box is functioning reasonably well . As to where all these other PMs have gone , remains a mystery ? None have
enquired about the ports, pipe or squish matters !

Moving on , by all means post the pipe and combustion chamber drawings , together with any notes which you
may feel appropriate to explain things , and i hope others might derive some small benefit from this information .


Regards , Trevor

blimey john im unsure what your trying to tell other than you havin load issues with computers.

Hi -Trevor thanks for the permission to post the two emails you sent me, I can only assure you I'm prety sure I sent a reply via PM, mind you I never know if or when people have recieved them, as its not possible to tell, if they have been read or got through.

I Know I get through to most when I get a reply back, saying OK OR tahnks or no yes or some others that I wish not to repeat!! for instance I know I sent out over 41 P.M. this week so far only recieved a few back, so Im really not sure who or what got through.

Mind you I have a few from the far east, offering all sorts of delights, but I would rather spend time getting exsited in the shed "working on my bike".

truth is I dont know where the p.m's went, all I know is "I sent them" ? prety sure about that.

anyway lets move on. !

all curtesy of Trevor Amos

Hi ED can you cut paste the skeche I sent you from trevor, for me, both the head and the combusion chamber, I sent you thats if it got through, I prity sure you know how to access my page on potobucket,

I think they are also in there. with the pipe info too, what a great little formula pipe this makes, if anyone wants to do the correlation its also interesting to note the similaritis between Trevors and George Todds information some 30 years earlier. if you can spot what I found!.

forgive me as I have omitted my question to Trevor, but sure from his answers and bible info below, you can make up your own minds what I was asking, a lot of Power in Trevors answers here, lots of gee gee's. !!! ignore these and you only going straight to jail with no get out card at the back of the grid, or sinply one way towards the back of the field.

Theory on combustion information
sent : from Trevor Amos for Derek Betts:-

The blending radius is simply , and in the case of the drawing , 1.5mm , the blend from the squish
edge to the start of the hemisphere of the chamber proper . As you can see the left hand rad with
only a 6mm wide squish band is the original , and is visibly larger , that is one reason for scaleing
up by 3x , to provide clarity . The date , of 1999 , shows the thinking of that era and we just copied
what we thought were the best bits from Honda practice . Sharp edges in combustion chambers
were then a complete no , no , it was felt certain to be a source of instant overheating and deto .
Today that fear has been laid to rest and chambers are now cut with the junction at the squish
edge merely de-burred with fine emery paper . Gas flowing over this edge will create turbulence
and that speeds up flame propagation , promotes efficiency and power goes up . The combustion
chamber is just about the only place where the more turbulence there is , the better will be the burn ,
it will also help with a slow burning fuel like Avgas .
It stands to reason that squish effects stop as the larger radius begins to take effect , this is shown
in the drawing with the two differing widths .

The taper to the squish band leaves a minimum of gas in the extremities of the chamber and that
enables a touch more gas to be in the chamber proper to be then burned and gain a little more
power . It is in any case doubtful if this remaining gas burns at all , but is quenched by the close
proximity of the , cooler , cylinder wall . As has been said before , the best squish band is one
leaving zero gas at tdc , no gas , no deto .

Hope that helps a little , Regards Trevor

----------------------------------------------------------------------------------------------
hope you enjoy, Ed should be along soon and post the sketches and drawings.

if you excuse my plunderting Trevor, the head shape and volume is of no consequence, !!!!!!!!!!

""""""""" but the "sharp edge" to the start of the "squish edge" and the little "taper" - is where its at - the real power and torque I mean,

regards Derek

Hi ed here is just fine. THANKS ED

As it forms part of "my returning to Bantam racing" so a good place, or we could add it to the expansion chamber topic,

I think it would have more weight here as my work on the dyno proved this adds 6hp if the engine tuning is good possibly more with others.
we have a little more than this now, so the future is bright "with orange-Trevor"

paramount, to get a good setup, taks loads of time, carb also for anyone nat already tuned in "Mick ABBEY" made this pipe, and the item I'm currently using what a brillinat job, he designed the secon around this pipe and our discussions on what I wanted where I needed the power, its certain has given me a but more,

I feel everything is different, so results will differ from engine to engine, but certainly a seat of pants improvment for anyone that I'm sure.

regards Derek

its seems to have been a while however, I have been busy so not had time for any more development, as sorting reliability issues, I seem to have this sorted I think, milaging parts is easy when your engine only pulls to 9500. seems they last for ever compared to pistons bearings stc.etc.

I will update with my findings on cracked frames and engine components and brackets, as it seems we have had quite a few since we rigidly mounted the exhaust, we tried a temp fix rubber cotton wheel at mallory that seems to be doing the job, as something has creacked at every meeting since we fitted the figgid mounted pipe, but not at mallory.

we tried the new rear shocks that need some adjustments.

I recieved this from George by email: I have been trying to trace the history of Bantam racing fairings.

(Derek - This was all so long ago, I'm hard pushed now to recall the history. Basically, there's no mystery about the fairing on the bike that Fred rode in the TT, and other national events. It was a continual development story over many long nights in the workshop at the back of Fred’s Raynes Park shop…

The picture showing Fred winning on #34 at Castle Comb was the initial version, a stock fairing from a racing goodies firm somewhere in the UK. You can see in the picture with Mole Benn, Roy Bacon and Fred that they all used this basic fairing…

We soon figured the airflow could be improved by covering underneath the engine with sheet aluminum, and this can be seen in the 1963 TT picture with Fred on #56.
The next development was an all metal version made by a workshop friend (Fred had so many contacts in London) seen in the Baluagh bridge picture (with #44).

This became the model for fiberglass molded version, which had a specially shaped entrance to the engine area (or tonsil as you call it) to smooth and concentrate air-flow over the cylinder. Instead of a sharp edge to the cut-away "tonsil", the form doubled back to make a classic air intake (see air intake pic #2).
Note also the shape under the top section to improve down flow onto the engine.

All this came out of my background in aircraft engines, but it was nothing more than logical thinking and the old adage "if it looks right…." Regarding wind tunnel tests, I have a faint recollection of there being something, ) to be continued-

Derek

Hi all - I need a left and right handed caliper, hyd- If anyone knows of a suitable bike I could go hunting for please let me know, they need to be as small as possible, but they need to be handed to. if anyone can suggest a bike I should look at "Nick or Mick Potter" ? you are both " motorcycle mechanics can you help me with this ! or anyone.

I had hopped to modify a set from a Minimoto, but my goodness, the quality of the alloy castings on the chinese copies of the twin disc setups are very poor, some one has suggested a scooter ? but which one ? anyone !!.

Progress is slow with eds Bike, we have been pushing ahead with it anyway. pic's of eds and my crank reed bike, WIP" also the sprinter is just in the photo, at the rear, dad recon's sprinting is a good place for experimenting and corelation between what we can measure and on how it performs atually on tarmack "with some one on board".

I found some really interesting details about pump and additives and ratings on available "and I stress the words legal - Fuels -

ED has decided to go back to colledge, to do carpentry, so that may put a stop on him racing, we will see for the time being, perhaps in the near future, or when things are ! more settled, still lots to do.

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"Please" no more attempted corrections" - "moving on"- please feel free to comment on the images.

Derek Betts

lydden was a mixed event for us we have still so much to try to make sure we have good correlation between the track and the dyno as it is not linear.

our snetterton woo's are behind us we are very happy we have returned the bike to a stable reliable condition. (14.8hp) after a slight adjustment to gearing and ignition timing (to 15.8hp) our fastest lap was posted in the second champ race on saturday, after this we used the rest of the weekend as development, its amazing what these little bikes will put up with in terms of comp ratio / ign timing running 100% avgas, but my goodness when you chanige or lower these, it alters the jetting by so much, we ran very rich in the first race on sunday, it seems our experiments tell us there is a large gap between what we see on the Dyno figures and track, but certainly there does seem to be some correlation between temp (under plug), the main jet - the tail pipe diameter and head volume that we tried between each outing, with pre set jetting from the dyno (all safe -on the rich side) what is confusing is the different to track to waht we have on the dyno from previouse runs, Ithink this may be because we had a failure of a major component since the last cadwell meeting taken some time to get it fixed, so as the dyno we use has been re-calibrated, this is possibly the reason why our jetting is out, different on the rich side. Hopfully we will have the new pipe finished for Darley !! and some testing to follow, before cadwell, I think after this I,m no longer going to make any more development changes. as the bike is quick enough I certainly still have a long way to go interms of corner speed Lyyden more than any meeting has shown this, but Rome was not built in one and half seasons,

I feel the meetings have been so well run, the snetterton meeting was great and I really enjoyed the barbeque on saturday evening it was great to see PT, like me Pete likes a drink Im not sure I understood or remeber the end however Ithink Mike mC donald found is real vocation in life Burning beef burgers, I spent some time chatting to one of the official/marchalls what a great guy, I never new these guys love what they do, he was so enthusiastic just as any racer is, what would we do without these volunteers.

I think its time we moved development on to our new/old bike for next year, as I certainly need something a bit quicker, taking account Im still re-learning my corner craft. I think next year will be interesting Like dan I can not wait till the next meeting.

regards to all Derek

P.S Rob !!!! my goodness man - "make sure you change those tyres" - slick's are not allowed in club racing lol.

Darley was a frustrating meeting, we could only make the sunday, un-avoidable. race one was great fun, the bike very rich, rain in race two saw me with my feet down too many times

heres a few pics to show next years project, and work for cadders.

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At a guess edd I take it as I can't see the kitchen and the amount of spares lol this is Derek's new pipe for caddwell????

Lol, that's fair comment! I believe it is, was just asked to put them up.


Eddie

I have not had a great deal of time lately, so I think a return! to my original post was in order".

a few questions / observations's/ and a request for info/help or a better understanding of how one should consider a change or implicate an improvement on a performance two stroke

"I often think "where do we go now we have a good strong set up in the quest for more power without affecting reliability and our Torque"

I have been a little pre-occupied recently due to a number of reasons, one is trying to do a house extention!! that's still WIP", i could not have picked a worst winter to attempt, Ive had little time for bikes tuning/development, or racing, and the new workshop and shed has still not been started,
but I did managed to get along to both of the first Classic and BHR meetings to view who was doing what, I spending most of the day watching from the comfort of my car in "the warm" and half hr in the pits catching up, this was about all I could stand in that cold wind.

This bit is for "Trevor" as per my recent PM's, I had been contemplating a change to piston port, bulding testing a barrel, but your last comment on here "on reeds" being the obvious best options for a 3 speed, and Colin agreeing with you, brings me to believe the best direction for me is another reed valve, I dont have the time to waste, and trying to get troque from a piston ported cylinder, experimenting on the length of trace iis tediu and very sesitive to change, perhaps this may be to do with the port shape as it opens, my latest creation's, (two barrels) and a btm end, one piston port although very strong top end, but only in the power curve of 2400 rpm's, (my weight) I feel its a "No No". may be one of the reasons why others
lost to another class, could never get their apparent missile of a bike to pull the skin off a rice pudding is down to the same thing perhaps if your on a pistin port and you want the bike to go fast you need to be under 10 stone, over this you just got to be on a 175 or a reed valver.


those under this and on 175 or on reedvalves should be banned! but lets not go there, so I have changed direction "again! and built a reed valve block to bolton the back of the piston prot cylinder, giving me two cylinders to experiment with, we have re engineered a completly new btm end, with a much improved crank shaft much stiffer crank cases, the crank has one piece flywheels and shafts affair, "the old crank" although beutifully made" appears to have been excessivly flexing, its possibly a design fault , although simple, it was clearly moving between shafts, flywheels and the rotational dowels that surposed to stop it moving, every time I CHANGED THE BIG END its alignment moved, I had it all loctited to stop it moving but it was then an absolute bitch to do anything with although it certainly improved the out of alignment problems Ihad every time Ipulled the cased apart, on the dyno just changing the crank, the bike at the back wheel gave more power, it also inproved the torque curve, a sign perhaps the crank was wipping and absorbing power.? I have a crank with a shorter ROD another Trevor suggestion, its also had some minor changes to the much more generiouse transfer ducts, (Ican get two fingers down the mains, bult in with the same blow down of 32deg, I converted to have the same "smaller flatter" exhaust port profile with suggested duct outter profile/restriction plate "not to be ditailed in open"(another Trevor Amos suggestion) anyway, on the first run we equalled what I had last year, as a starting base, we are still looking for extra HP/Torque.

I'm looking to elivate this output to a competertive state for my weight, its my belief to actually win a race, we would need a performance around
about 25/26 hp and 15ftlbs torque to compete against someone thoughs who weighs in at 7/8/9 stone and have 20/21 hp at the back wheel with 11/12 ftlbsmax. (perhaps 1 or 2 have a little more than this, but not much more)!.

so my next question is, where should my development/experiments go, and how does one think before one can start to identify what should /must be changed or tried to make an improvment, im sure there are many new starters who would like to understand how does a development Engineer think!.

For the record my current set up is now such that I have possibly the biggest and most square exhaust port than I have ever had, ? do I make it bigger or try another front pipe in the quest for more power.

Do I increase the head comp ratio, certainly boosts both torque, I have found this to limit or arrests the rev ceiling. ( I have converted a new MZ head to tryout with a very special combuston shape chamber ala DKW)

maximum power is still only at 10,000. or just a little under, so do I look for more revs ! try a bigger carb again perhaps.

or do I simply stay with it as it is and accept possibly this is as good as it gets.! hoping with good reliability an opportunity will arrise to improve my craft enough to get a good feeling with the whole package to compete/win at the front. "I think not", I need more HP and to maintain the current torque we have.

I noticed the lap times at Mallory where not that quick, although some did seem to be going quickly in reality the lap time said not any quicker certainly no where near the time done a few years ago !.

my currnet engine set up details are as follows
current port timings
95 exhaust (35.5mm width cordal) (98 advised)
63 transfer (23mm wdith square/flat sides) (65 advised)
reed inlet with third port (20mm width) (22mm advised)
exhaust dimesiion from on my current and best race results, are from the formula pipe on the Tervor Amos design on this forum.
carb 30.0mm, with the power jet blocked off. (32.0mm, 34.0mm to try)
red valve yz 1981 with fenolic pettles, boycen, with home built reducer/stuffer between carb and reed valve. (1980's vintage)

I run avgas, 50/50, so far avoided the extremly toxic "race fuels" that are available that allow much higher comp/ignition retard. the cost of this is not much more than avgas at £4 per ltr it hardly seems worth it. (interestingly those runnig these should have a sign on there seat not to sit behind in the collecting area telllig you so !!!!!!!!!.


problem areas we have experienced/resolved or to resolve:-
Ive been looking to Mick Potters advice, changing my tyres, my 23 year old front tyre, and my 16 year old tyre on rear, suggested as outclassed by current and new rubber, however I could not help notice any cornering difference when comparing to others at the last meeting around/behind me "who were on NEW fresh rubber". " so a cuple of hand me downs (greatfully recieved) will be on at the next meeting.

Ignition we have been advised is the way to get on terms with the few infront, so as I'm still on a fixed curve ignition we have tried out our new system, although some issues with set up, Rob seems to have his working reliably, but problems with our trigger setup inside the primary chain case, where i had put it to allow me to run without the extra friction of a timing side seal, caused too many problems, so its been put on the back burner for now, I had planned to redesign the cover, that has some very complex kit on the inside and manufature a better solution, but time / and the importance of reliability means it has to wait for now.

any assistance including suggestions or comments, drawings are very welcome.

Derek

Derek ,
You want easier starting , more low down torque , more top end with over rev , all of which will make the pipe work harder for you through the whole rev range , and result in a genuine win , win situation ?? If the answer is yes , then junk the straight line ignition system and treat your self to a retarding set up ! Programmable is good but throws up so many combinations that you might end up going around in circles . It works for me , so it will work for you , this is the 21st century after all !

More later , Trevor

yes "I want" - I have a suitable ignition, its one Alan Brown help me get and partly set up, Alan knows quite a lot about these, Ive not raced with it yet, its absolutly the business, it terms of its simpleness to change but to set up I have not really the confidence with it on what im doing with it, but like I said before "its just a bit of time". I think its one of those systems that need a track day afternoon to set up properly, in terms of the wiring switching, location of the fuses, and the length of wires all seem to effect it etc etc can not imagine trying it out at a race meeting. !

Always seems to be "a but" -

But I feel I over engineered its set up, trying to gain another advantage that I first found by mistake by fitting the wrong size timing side seal, a 20mm seal on a 19mm shaft, at one of my last race meetings, I managed to split the bridgestones at the front at the fastest circuit Ihave raced in the UK, with a 3rd place in a field of 200cc 5/6 speeders some with twin cylinder and disc valves memories!. actually my bike was also very fast I always attribute it to this lack of friction, on the timing side seal, (and a bit of hard agressive rast safe! riding that i know Im still capable of especially after last year)

the latest figures on the dyno I sent you are the engine run without this side seal in. !!!!

so back to the issue- yes I want more" more" more", but who does'nt.

regards Derek

Panic not Derek!!
I will help you set the ignition up when you are ready, you will be surprised how easy it all is!
Cheers!!
Alan

Hi Alan

Many thanks for this offer of help I would certainly like to take you up on it, I had been trying to do it myself, I think if I had put it in a convention place it would be working ok, but,

Like I said I had set it up under the primary cover in a round about fashion, it appeared to work quite to begin with, well even with the oil splashing around, but the plate holding it came lose and it got chewed up in the primary chain. ouch Robbie's lovely primary chain made mince meat of the hole assembly before it punched a hole in the front of the cases as it came to a stop, giving me a mouth full of oil. (Primary chain still looks great thou!!)

I had a re-think, I pickup up a new censor last week to try again, same item from R.S and want to try again, but this time I'm going to fit it on the end of the crank nut machined and welded/brazed affair, that will protrude into a D10/14 ignition compartment, some issues here to resolve like getting the cover off without having to take the nut/plate off the end of the crank, need to machine it to allow a separate cover outside covering it all in say two elongated holes to allow movement if required, bit I'm pretty sure it does not need it, as it can be adjusted with the program, to secure any oil coming out or building up under it the small original end cover the air hole plugged with a drain back inside into the btm lower side of the compartment, these work inside F1 gearboxes so it should work like this "well it did for about 15 min's".

its all WIP, I think I have no where else to go other than this mod, at the moment, as I do not want fit it in a convention location as the seal just gives too much drag, a mod that should not be allowed for 175cc class or ! .
will PM you some pictures if I can, Ill give you a call when its done, perhaps you can help with the wiring all strung over the bike the last time also fuse position, it kept blowing, twice, I think its sensitive to vibration ? or just not a very good contact some where in wiring. !

kind regards Derek

Most of the problems with something as complex as this tend to be connections, and the quality of them. Hopefully you are using good gear and really take your time to get each connection perfect and crimped nicely, plus use good vehicle wires. It is something I found out too!
Once it is correct it stays that way!
I fitted 002 with the same system for Chris Bennion, and it has been solid, but it did take a fair bit of time and effort.
Cheers,
Alan